Handheld power tool with low speed

ABSTRACT

A handheld power tool with low speed includes a housing, a middle sleeve shell and a front sleeve shell connected by threads on the exterior, and a pneumatic motor, a planet gear mechanism, a bearing, a cushion member and a fastened base in the interior. The pneumatic motor connects the planet gear mechanism through a driving shaft. The planet gear mechanism connects a grinding member located in the fastened base through a driven shaft and a flexible shaft. An outer flange portion is disposed around the fastened base. An inner flange portion is disposed on the front sleeve shell in order to press the outer flange portion while the middle sleeve shell is locked by the front sleeve shell so that the fastened base, the cushion member, the bearing, the planet gear mechanism and the pneumatic motor are fixed in a row.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a handheld power tool and more particularly to a handheld power tool turning at a low speed.

2. Description of Related Art

A small handheld grinding tool can be used to grind surfaces of specific objects. Such a handheld grinding tool includes a motor and a grinding member whose working angle is adjustable. A flexible shaft is provided between the motor and the grinding member in order to transmit the power output by the motor to the grinding member.

However, the motor rotates so fast that the flexible shaft suffers a lot of wear and tear during rotation since it is not rigid. The flexible shaft is often broken and then must be replaced. On the other hand, the grinding member rotates at a high speed equal to that of the motor so that the object surfaces are worn down fast and become over-ground under an operation fault.

BRIEF SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a handheld power tool with low speed that causes a lower wear and tear to the shaft to elongate service life. Moreover, the power tool of the present invention is easy to be operated and capable of preventing object surfaces from over-ground.

To achieve the above objective, the present invention provides a handheld power tool with low speed that includes a housing having a first opening with a first outer thread portion at an end thereof. A pneumatic motor with a driving shaft extending out of the first opening is disposed in the housing. A middle sleeve shell has a second opening and a third opening at two ends thereof. The second opening is provided with a first inner thread portion to be fit with the first outer thread portion of the housing. The third opening is provided with a second outer thread portion. A planet gear mechanism disposed in the middle sleeve shell includes a gear base provided with a plurality of planet gears and a gear circuit surrounding the gear base. Each of the planet gears is engaged with the driving shaft and the gear circuit respectively. The gear base is provided with a driven shaft extending out of a bearing that is adjacent to the gear base. A cushion member disposed in the middle sleeve shell has an end that is adjacent to the bearing and an opposite end extending to the third opening. The cushion member has a shaft hole provided with a coupling member connected between the driven shaft and a flexible shaft extending out of the third opening. A fastened base that is adjacent to the cushion member has an outer flange portion disposed around a periphery of the fastened base. A front sleeve shell has a fourth opening and a fifth opening at two ends thereof. The fourth opening is provided with a second inner thread portion to be fit with the second outer thread portion of the middle sleeve shell. The fifth opening is provided with an inner flange portion that presses the outer flange portion while the middle sleeve shell is locked by the front sleeve shell so that the fastened base, the cushion member, the bearing, the planet gear mechanism and the pneumatic motor are fixed in a row. A side ring is disposed adjacent to the front sleeve shell. A grinding member connected with the flexible shaft includes a head portion for grinding objects, a neck portion connected to the head portion and a ball-shaped base connected to the neck portion. The ball-shaped base is provided with a pivot shaft to pivot on the fastened base for swinging so that a working angle of the grinding member is adjustable. The neck portion extends out of the side ring and is provided with a regulating portion for displaying an orientation of the grinding member. A control ring is disposed around the fastened base for locking the working angle of the grinding member.

In addition, the middle sleeve shell is provided with an assembly ring for coupling with an auxiliary handle.

In one embodiment, the regulating portion is a flat plane cut from an arc surface disposed on the neck portion.

In one embodiment, the fastened base is provided with a recess for accommodating the ball-shaped base. The ball-shaped base is pivoted in the recess by the pivot shaft. A plurality of grooves are disposed on the ball-shaped base. Each of two opposite sides of the recess is provided with a through hole accommodating a ball that can move along the through hole. The fastened base is surrounded by a C-shaped ring with two abutting portions disposed on an inner surface of the C-shaped ring. The C-shaped ring is surrounded by the control ring and is forced to open or close by turning the control ring. While the C-shaped ring is closed, the abutting portions push the balls so that the balls abut against the ball-shaped base in the groove in order to fix the grinding member. While the C-shaped ring is open, the abutting portions do not push the balls so that the grinding member can swing for adjustment to the working angle.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of the present invention;

FIG. 2 and FIG. 4 are exploded perspective views of the first embodiment of the present invention;

FIG. 3 is a sectional view of the first embodiment of the present invention;

FIG. 5 and FIG. 6 are sectional views showing the grinding member is fixed when in use; and

FIG. 7 is a perspective view of a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1-FIG. 3, the handheld power tool with low speed according to a first embodiment of the present invention includes a housing 11, a middle sleeve shell 12 and a front sleeve shell 13 connected by threads on the exterior, and a pneumatic motor 2, a planet gear mechanism 3, a bearing 33, a cushion member 4 and a fastened base 5 in the interior.

A first opening 111 with a first outer thread portion 112 is disposed at an end of the housing 11. The pneumatic motor 2 is accommodated in the housing 11. A driving shaft 21 of the pneumatic motor 2 extends out of the first opening 111.

A second opening 121 with a first inner thread portion 123 and a third opening 122 with a second outer thread portion 124 are disposed at two ends of the middle sleeve shell 12 respectively. The middle sleeve shell 12 couples with the housing 11 via the connection of the first outer thread portion 112 and the first inner thread portion 123. An assembly ring 14 is disposed on the middle sleeve shell 12 for coupling with an auxiliary handle (not shown in the figures).

The planet gear mechanism 3 is accommodated in the middle sleeve shell 12, including a gear base 31 and a gear circuit 32. The driving shaft 21 goes into the gear base 31. The gear base 31 is provided with three planet gears 311 located around the driving shaft 21. Each of the planet gears 311 engages with the driving shaft 21. The gear circuit 32 surrounds the gear base 31 and engages with the three planet gears 311. A driven shaft 312 extends from the gear base 31 and passes through the bearing 33 that is adjacent to the gear base 31. Accordingly, when the driving shaft 21 of the pneumatic motor 2 rotates, each of the three planet gears 311 is driven to rotate respectively. Meanwhile, the three planet gears 311 circle the driving shaft 21 since the gear circuit 32 is fixed. Therefore, the gear base 31 and the driven shaft 312 are driven to rotate. A rotation speed of the driven shaft 312 is less than that of the driving shaft 21 since the tooth number of the planet gear 311 is less than that of the gear circuit 32.

The cushion member 4 is disposed adjacent to the bearing 33 so that an end of the cushion member 4 extends to the third opening 122 because a total length of the planet gear mechanism 3 and the bearing 33 is less than that of the middle sleeve shell 12. The cushion member 4 has a shaft hole 41 provided with a coupling member 34. The driven shaft 312 goes into the shaft hole 41 and connects the coupling member 34. A flexible shaft 35 is connected with the coupling member 34 and extends out of the third opening 122.

The fastened base 5 located adjacent to the cushion member 4. An outer flange portion 52 is disposed around a periphery of the fastened base 5. A fourth opening 131 with a second inner thread portion 133 and a fifth opening 132 with an inner flange portion 134 are disposed at two ends of the front sleeve shell 13 respectively. The front sleeve shell 13 couples with the middle sleeve shell 12 via the connection of the second inner thread portion 133 and the second outer thread portion 124, and meanwhile the inner flange portion 134 abuts against the outer flange portion 52.

With the middle sleeve shell 12 being locked by the front sleeve shell 13, the inner flange portion 134 presses the outer flange portion 52 firmly. The pressure passes down through the fastened base 5, the cushion member 4, the bearing 33, the planet gear mechanism 3 and the pneumatic motor 2, and then objects abovementioned are fixed in a row. In addition, a side ring 15 is disposed adjacent to the front sleeve shell 13.

The fastened base 5 is provided with a recess 53 for accommodating a grinding member 6. The grinding member 6 includes a head portion 61 for grinding objects, a neck portion 62 connected to the head portion 61 and a ball-shaped base 63 connected to the neck portion 62. The ball-shaped base 63 is pivotally assembled in the recess 53 with a pivot shaft 51 and is connected with the flexible shaft 35. Accordingly, the ball-shaped base 63 is able to swing so that a working angle of the grinding member 6 is adjustable.

The neck portion 62 extends out of the side ring 15 and is provided with a regulating portion 622 for displaying an orientation of the grinding member 6. In detail, the neck portion 62 is provided with an arc surface 621 while the regulating portion 622 is a flat plane that is cut on the arc surface 621. When assembling, operators can easily adjust the orientation of the regulating portion 622 by visual interpretation since the regulating portion 622 is not covered by other objects. With the orientation of the grinding member 6 is well adjusted, the swing direction of the grinding member 6 can be matched up with a position on the housing 11 where a switch 113 of the pneumatic motor 2 locates so that users can operate the handheld tool conveniently.

After adjusting the working angle of the grinding member 6, it can be positioned by a control ring 8 disposed around the fastened base 5. As shown in FIG. 4, a plurality of grooves 64 are disposed around the ball-shaped base 63. Each of two opposite sides of the recess 53 is provided with a through hole 54 accommodating a ball 55 that can move along the through hole 54 when being pushed. A C-shaped ring 7 surrounds the fastened base 5 and has two abutting portions 73 disposed on an inner surface of the C-shaped ring 7. The control ring 8 includes a circular outer surface 81 with a skidproof pattern 811 and an inner surface 82 surrounding the C-shaped ring 7.

The C-shaped ring 7 is forced to open or close by turning the control ring 8. While the C-shaped ring 7 is controlled to open, the abutting portions 73 leave the balls 55 and do not push the balls 55 so that the balls 55 do not press on the ball-shaped base 63. Accordingly, the grinding member 6 can swing for adjustment to the working angle, as shown in FIG. 5 and FIG. 6.

While the C-shaped ring 7 is controlled to close, the abutting portions 73 engage and push the balls 55 so that the balls 55 abut against the ball-shaped base 63 in the groove 64. Therefore, the grinding member 6 is fixed so as to determine the working angle.

The present invention features a lower damage to the flexible shaft 35 than the prior art due to the rotation speed of the flexible shaft 35 being lowered by the planet gear mechanism 3 so as to elongate the service life. In addition, the grinding member 6 is driven by the flexible shaft 35 with a lower rotation speed so that the object is ground slowly. Users have more time to operate the tool till the grinding work is completed, which preventing the object from being over-ground under an operation fault.

What is shown in FIG. 7 is a second embodiment of the present invention. In this embodiment, the control ring 9 includes a buckle 91 to control the grinding member 6. The working angle of the grinding member 6 is adjustable if the buckle 91 is released while the working angle of the grinding member 6 is fixed if the buckle 91 is locked. 

What is claimed is:
 1. A handheld power tool with low speed comprising: a housing having a first opening with a first outer thread portion at an end thereof, a pneumatic motor with a driving shaft extending out of the first opening disposed in the housing; a middle sleeve shell having a second opening and a third opening at two ends thereof, wherein the second opening is provided with a first inner thread portion to be fit with the first outer thread portion of the housing, and the third opening is provided with a second outer thread portion; a planet gear mechanism disposed in the middle sleeve shell including a gear base provided with a plurality of planet gears and a gear circuit surrounding the gear base, wherein each of the planet gears is engaged with the driving shaft and the gear circuit respectively, and the gear base is provided with a driven shaft extending out of a bearing that is adjacent to the gear base; a cushion member disposed in the middle sleeve shell with an end being adjacent to the bearing and an opposite end extending to the third opening, wherein the cushion member has a shaft hole provided with a coupling member connected between the driven shaft and a flexible shaft extending out of the third opening; a fastened base adjacent to the cushion member with an outer flange portion disposed around a periphery of the fastened base; a front sleeve shell having a fourth opening and a fifth opening at two ends thereof, wherein the fourth opening is provided with a second inner thread portion to be fit with the second outer thread portion of the middle sleeve shell, and the fifth opening is provided with an inner flange portion that presses the outer flange portion while the middle sleeve shell is locked by the front sleeve shell, whereby the fastened base, the cushion member, the bearing, the planet gear mechanism and the pneumatic motor are fixed in a row; a side ring disposed adjacent to the front sleeve shell; a grinding member connected with the flexible shaft including a head portion for grinding objects, a neck portion connected to the head portion and a ball-shaped base connected to the neck portion, wherein the ball-shaped base is provided with a pivot shaft to pivot on the fastened base for swinging so that a working angle of the grinding member is adjustable, the neck portion extends out of the side ring and is provided with a regulating portion for displaying an orientation of the grinding member; a control ring disposed around the fastened base for locking the working angle of the grinding member.
 2. The handheld power tool with low speed of claim 1, wherein the middle sleeve shell is provided with an assembly ring for coupling with an auxiliary handle.
 3. The handheld power tool with low speed of claim 1, wherein the regulating portion is a flat plane cut on an arc surface disposed on the neck portion.
 4. The handheld power tool with low speed of claim 1, wherein the fastened base is provided with a recess for accommodating the ball-shaped base, the ball-shaped base is pivoted in the recess by the pivot shaft; a plurality of grooves are disposed on the ball-shaped base; each of two opposite sides of the recess is provided with a through hole accommodating a ball that can move along the through hole; the fastened base is surrounded by a C-shaped ring with two abutting portions disposed on an inner surface of the C-shaped ring; the C-shaped ring is surrounded by the control ring and is forced to open or close by turning the control ring; while the C-shaped ring is closed, the abutting portions push the balls so that the balls abut against the ball-shaped base in the groove in order to fix the grinding member; while the C-shaped ring is open, the abutting portions do not push the balls so that the grinding member can swing for adjustment to the working angle. 